The present invention relates to an apparatus for the manufacture of corrugated pipes from thermoplastic in which mould segment halves, which complement one another in pairs, are guided together in a circuit along a mould path adjacent to an injection head, are moved apart at the end of the mould path and are returned back to its start separately from one another, comprising a mould path device to move the mould segment halves along the mould path and a return conveyor to convey the mould segment halves from the end of the mould path back to its start, with the mould path device comprising a machine table having a lower guide and lower drive means for the mould segment halves and a cover frame secured to the machine table having an upper guide and upper drive means for the mould segment halves.
With such corrugated pipe plants of the so-called shuttle type, return conveyors moving to and fro are used. The return conveyors can have a gripping arm which grips a mould segment half located at the end of the mould path, travels to the start of the mould path, sets the mould segment half down there and again travels back to the end of the mould path in order to grip the next mould segment half again. On the actual mould path, the mould segment halves are moved along by separate drives which are disposed on the machine table, on the one hand, and at the cover frame disposed thereabove, on the other hand. It is in particular known in this connection to provide driving pinions in the machine table and the cover frame disposed thereabove which engage in racks disposed at the top and at the bottom at the mould segment halves and which move these forward correspondingly.
A corrugated pipe plant of the shuttle type is known from EP 0 764 516 A2. In this, a gantry crane is anchored on a base plate on which the mould path is disposed or the mould segment halves are displaced along the mould path. Carriages which can travel in opposite directions are mounted at a conveying bridge which engages over the mould path device, is formed in a slightly V-like shape and lowers towards the centre, said carriages being secured at gripping arms for the mould segment halves. When the carriages on the V-shaped conveyor bridge are moved apart, the mould segment halves are moved apart transversely to the mould path and thereby simultaneously raised. This known plant, however, has disadvantages in a number of respects. On the one hand, the plant is not very variable. Without fairly large conversion work, it is fixed to one mould segment half size, with which the gantry crane is coordinated with its gripping arms with respect to height and to which the mould path device as such is matched with its upper and lower toothed profile drives. On the other hand, use at different production locations can only be achieved with a large assembly effort for the taking down and setting up of the plant. Moreover, the plant is specifically disadvantageous with respect to the main drive for the mould segment halves along the mould path. The arrangement of the driving pinions and racks at the machine table and at the cover frame or at the lower side and the upper side of the mould segment halves is prone to error with respect to tolerances which can arise, for example, due to thermal expansion of the mould segment halves.
A corrugated pipe plant is furthermore known from WO 94 076 73 in which the mould segment half pairs are combined in two groups. A first group is mounted on a carriage which can be travelled to and fro on a lower support frame. A second group of mould jaws is mounted on a carriage which can be travelled to and fro on an upper carrier frame. The mould segment halves can in this connection each be travelled apart and together on the carriage. To move the mould segment halves back, they are first travelled apart on the carriage, then the carriage with the mould segment halves which are travelled apart is travelled past the mould segment halves of the other carriage back to the start of the mould path and, finally, the mould segment halves on the carriage are again travelled together. This apparatus is, however, less suitable in practice since a plurality of mould segment halves always has to be travelled apart at one time so that de facto only a very short mould path is available.